0 Assigned ID: 1035 ----- Attempting Submission 1 (Fri Apr 11 23:17:59 GMT 2014) ----- HST Phase I Proposal 1035 (crater.apt) successfully submitted. we added preflash to the WFC3 F390M as per STSCI's suggestion -1009413684 ----- Attempting Submission 1 (Wed Jul 23 22:18:21 GMT 2014) ----- HST Phase II Proposal 13746 (crater_July23_2pm.apt) successfully submitted. ----- Attempting Submission 2 (Fri Jul 25 20:38:21 GMT 2014) ----- ----- Attempting Submission 3 (Mon Aug 25 20:36:28 GMT 2014) ----- Is the Crater satellite the Milky Way's Smallest Dwarf Galaxy or its Largest Globular Cluster? We propose deep ACS/WFC3 photometry that will reveal the nature and origin of the Galactic satellite known as 'Crater'. Crater exhibits properties intermediate between dwarf galaxies and globular clusters. As a dwarf galaxy, Crater would be the smallest and least massive known in the Galactic halo. As a globular cluster, Crater would be the largest and most distant. Our photometric observations will tell the age, metallicity, limits on metallicity spread, mass function and dynamical state of Crater's stellar population(s). We will use this information to distinguish whether Crater is 1) a dwarf galaxy that formed in a dark matter potential, or 2) a globular cluster that has grown to its current size via internal dynamical evolution. In either case, we will learn what mechanisms are responsible for Crater's extreme properties. This proposal is to obtain deep imaging in two filters, and imaging to ~V=24.5 in two filters for the newly discovered Crater globular cluster. A minor modification was made to the published central coordinates to help to avoid the two very bright field stars. In addition, small pos-targs refined the position, a different POS-TARG for the WFC3 field snd for the ACS field. The primary goal of visit 1, one orbit, is to get deep imaging with WFC3 in F390M. There are ORIENT constraints to avoid the two bright stars(the WFC3 FOV is smaller than the ACS below). The primary goal of visit 2, 4 orbits, is to get deep imaging with ACS in F606 and F814. We also obtain short exposures in F555 and F814 and F606. There is a small pos-targ difference in exposure 3 of visit 2 so that the two short F555W exposures have dithers between them. The F555 data is to match the F390 WFC3 data, and allows us to use a previous calibration to obtain metallicities of stars in this object. We apply some ORIENTS to avoid the two bright stars. the ORIENTS are a bit stringent in order to ensure that we avoid bright stars AND get all of Crater at all orients. RESOLVED STELLAR POPULATIONS Default false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER J2000 J2000 STELLAR CLUSTER GLOBULAR CLUSTER J2000 WFC3/UVIS Imaging No No F390M ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F555W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F814W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F555W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 1 false POS-TARG DITHER 3.011 LINE false false 3 85.28 ACS-WFC-DITHER-LINE 2 false /tmp/OPVisit3835972502495023045.xml The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. 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